Swarm Takes LoRa Sky-High
There are plenty of reasons to deploy an Internet of Things (IoT) network in a rural area. But connecting dozens or hundreds of sensors to a network can also be a nightmare. Wind turbines or oil wells benefit from sensors measuring their respective environments and performance, but their operators should count themselves lucky if such energy harvesting facilities happen to be in range of robust cellular networks so they can stay connected to the Internet. The same is true of cargo containers crossing an ocean on a ship; they could be easily tracked with individual identifying devices, but at sea, they need satellites to transmit and receive signals at all.
Traditionally, there hasn't been a good option for connecting low-power, low-data devices to the Internet en masse when they're in an area without good coverage. Satellite services tend to be expensive: Most cost on the order of US $1 to send the amount of data roughly equivalent to that in a text message. Hundreds of IoT devices sending equivalent amounts of data as status updates, multiple times per day or even multiple times per hour, would break the bank.
Swarm, a satellite start-up that uses CubeSats about the size of a grilled cheese sandwich to provide IoT coverage, has instead developed a satellite network specifically for IoT networks that would otherwise struggle to connect to the Internet. To do so, the company has adapted the popular IoT wireless standard LoRa, turning the terrestrial technology into a high-flying-and even longer-ranging-solution.
Swarm's tiny satellites previously placed the company in hot water with the U.S. Federal Communications Commission (FCC) when Swarm launched four initial satellites without the agency's permission. The FCC had denied Swarm the right to launch the satellites because of the agency's concerns that the satellites were too small to be effectively tracked-but still large enough to cause serious damage if they collided with another object in orbit. As IEEE Spectrum reported at the time, the FCC gave the company the dubious distinction of being behind the first illegal satellite launch in history. After a US $900,000 fine and a compliance plan to make its satellites safer and easier to track, Swarm has begun to realize its LoRa-based satellite network.
LoRa, if you're not familiar, is a wireless communication method managed by California-based semiconductor and chip manufacturer Semtech. LoRa is specifically designed for massive-scale IoT deployments. The name is short for, very simply, Long Range." The wireless standard sends data in small bursts, similar in size to a text message, which makes it perfect for devices that need to send plenty of status updates or a regular stream of measurements. The technology is also designed to require very little power, so that it does not drain the batteries of IoT devices too quickly. But LoRa was still very much designed for terrestrial networks, where devices and gateways would be relatively stationary with respect to one another.
When Swarm was considering what communications technology to use for its constellation of satellites, the company quickly realized that traditional satellite technologies wouldn't work. Not without approaching the high costs of existing providers like Iridium, Globalstar, or Inmarsat. We have a limited amount of power on the ground, and a limited amount of power in space. And with the coverage that we wanted and the link budget that we wanted to achieve, LoRa won that trade," says Ben Longmier, the company's chief technology officer.
We had to tweak some of the settings to make it appropriate," Longmier adds. We have satellites that are moving at 7.4 kilometers per second [16,550 miles per hour]." The rapid speed of Swarm's satellites means that the signals they send and receive are subject to Doppler effects that distort them.
The distance was also a challenge. LoRa, as its name implies, is designed for the long distances covered by a wide IoT deployment. But even the most expansive deployments come nowhere close to the distances that satellite signals need to cover. Swarm's satellites zip past the Earth at an altitude of 550 kilometers. And that's the distance when a satellite is directly overhead. If it's looking down at a slant range, or at the horizon, that can be as long as 2700 kilometers, 2900 kilometers," says Longmier. That's like from Los Angeles to Chicago." What's more, Swarm's satellites are transmitting signals over that distance using the amount of signal power used in a wireless garage door opener.
Because of the unique circumstances under which Swarm needs to transmit, Longmier says the company couldn't use LoRaWAN, the standard network protocol for LoRa. Instead, the company wrote custom networking protocols.
The company also fine-tuned several radio components to make it possible to send and receive LoRa signals over such long distances. The CubeSats, for example, carry extremely sensitive low-noise amplifiers and preamplifiers to boost the weak signals upon arrival, making them easier to decode before the satellite retransmits them to a ground station elsewhere on the planet.
Photo: Swarm This miniature Swarm Tile connects an IoT device to the Swarm Network. Swarm's full 150-satellite constellation has not been fully deployed yet, but Longmier says the company already has customers receiving continuous coverage from the satellites currently in orbit. The company has also started selling customers low-power modems that are optimized to connect with the CubeSats and provide a more robust connection. Put together, Swarm is betting that LoRa has astronomical potential.
This article was edited on 24 March 2021, to correct Semtech's location.